Natural attenuation of chlorinated solvents: a comparative study

Sites contaminated by chlorinated solvents have been investigated. Sites Dolni Tresnovec and Zetor located in Czech Republic exhibit relatively reducing conditions. Primary chlorinated solvents are attenuated by reductive dechlorination processes, and plumes have probably reached steady-state at Zetor site. Terminal electron accepting processes (TEAP) are ferric iron reduction and sulfate reduction at respective Dolni Tresnovec and Zetor sites. Source of organic matter at Dolni Tresnovec site is the waste deposited at local landfill. At Zetor site reducing conditions are linked to the petroleum hydrocarbons spill from broken pipeline. In contrast, site Dubnica in Slovak Republic exhibits oxidizing conditions, and natural attenuation of chlorinated solvents occurs mostly by dispersion. Modeling by the program BIOCHLOR indicated formation of steady-state plumes close to source at Zetor site, much longer steady-state plumes at Dolni Tresnovec site, and extremely long plumes at Dubnica site. Results demonstrate an important role of redox conditions in natural attenuation of chlorinated solvents.     

Geoinformatics in morphological study of River Paglia,Tiber River basin,Central Italy

This work reports the results of a geomorphological study on the River Paglia (Tiber basin, Central Italy), to analyse the historical evolution of the riverbed/floodplain system in its lower valley reaches, upstream the confluence of River Tiber. A morphological–sedimentological approach has been used, starting with an historical analysis and a survey of the forms and sediments in the riverbed/alluvial plain system, in order to reconstruct the current evolutionary trend and to identify the causes and processes leading to changes in natural trends. This approach is not in contrast to the hydrologic–hydraulic one, normally applied in engineering fields, but it is integrated with it in a complementary and parallel manner, in order to achieve the complete knowledge of the river system, result of an investigation multidisciplinary, aimed to define its physical state. Historical data (cartographic documents, digital terrain models—DTM, topographic surveys, aerial photographs, etc.) indicate clear-cut narrowing and deepening of the active channel, manifested after the Second World War and due to the considerable changes which affected the entire fluvial system (from the recovery of land for agriculture near the river, to sediments taken from its bed over the past few decades). The result is a state of great disequilibrium, which is shown in the passage from a braided morphology, observed in the 1950s, to a single channel with low sinuosity (wandering type). This type of morphology is certainly more unstable: in fact, the narrowing and deepening of fluvial sections provide a better hydraulic efficiency for the upstream, so the peak discharge does not overflow. Such peak discharge arrives downstream, next to the confluence with the Tiber River, not laminated, causing serious flooding effects. An increased vulnerability is observed in the last reach, in the areas pertaining to the river, where most of the industrial-economic activities are concentrated and where transportation infrastructures of nationwide importance (Italy’s most important motorway, the A1, and the Rome–Florence–Milan high-speed rail links) are located. The evolution of the Paglia (which is not substantially different from that of many streams in Italy and in general throughout Europe) is affected by severe anthropic constraints and intense exploitation of resources, which have produced a state of disequilibrium approaching irreversibility in an already vulnerable system. Finally, some suggestions for the correct management of the river system are pointed out, with the aim of mitigating the flood risk in the lower Paglia valley.     

Dissolved load of the Loire River: chemical and isotopic characterization

The Loire River, with one of the largest watersheds in France, has been monitored just outside the city of Orleans since 1994. Physico-chemical parameters and major and trace elements were measured between 2-day and 1-week intervals according to the river flow. The sampling site represents 34% of the total Loire watershed with 76% silicate rocks and 24% carbonate rocks.

Elements are transported mainly in the dissolved phase with the ratio of total dissolved salts (TDS) to suspended matter (SM) ranging between 1.6 and 17.4. Chemical weathering of rocks and soils are thus the dominant mechanisms in the Loire waters composition. The highest TDS/SM ratios are due to dissolved anthropogenic inputs. The database shows no link between NO₃⁻ content and river flow. The Na⁺, K⁺, Mg²⁺, SO₄²⁻, and Cl⁻ concentrations are seen to decrease with increasing discharge, in agreement with a mixing process involving at least two components: the first component (during low flow) is concentrated and may be related with input from the groundwater and sewage station water, the second component (during high flow) is more dilute and is in agreement with bedrock weathering and rainwater inputs. A geochemical behaviour pattern is also observed for HCO₃⁻ and Ca²⁺ species, their concentrations increase with increasing discharge up to 300 m³/s, after which, they decrease with increasing discharge. The Sr isotopic composition of the dissolved load is controlled by at least five components — a series of natural components represented by (a) waters draining the silicate and carbonate bedrock, (b) groundwater, and (c) rainwaters, and two kinds of anthropogenic components.

The aim of this study is to describe the mixing model in order to estimate the contribution of each component. Finally, specific export rates in the upper Loire watershed were evaluated close to 12 t year⁻¹ km⁻² for the silicate rate and 47 t year⁻¹ km⁻² for the carbonate rate.     

Archaeological site distribution by geomorphic setting in the southern lower Cuyahoga River Valley,northeastern Ohio: Initial observations from a GIS database

In this study, we compiled unpublished archival documentation of archaeological site locations from the southern part of the Cuyahoga River Valley in northeastern Ohio, USA, registered at the State of Ohio Historic Preservation Office into a Geographic Information Systems (GIS) database. Using digitized soil shapefiles to generate a geomorphic data layer, we assessed the spatial and temporal distribution of 79 known archaeological sites by landform association. This digital compilation indicates that Woodland period, Late Prehistoric, and Historic sites occur in most geomorphic settings along the river valley. In contrast, Paleoindian and Archaic sites only occur on Wisconsinan cut terraces and in upland interfluve settings, indicating that most of these documented sites are in primary contexts and have not been reworked. We discuss the distribution of archaeological sites in the study region as a function of various factors, including cultural activities, taphonomic processes, landform development, and the nature and extent of the original archaeological surveys. Observed spatial patterns of known sites clearly reflect local geomorphological controls; artifactual contexts from the earlier prehistoric periods are underrepresented in the database. We conclude that additional site surveys, as well as the excavation and documentation of new sites in this part of Ohio, are required to understand local prehistoric economies and to ascertain patterns of culturally mediated land use. © 2004 Wiley Periodicals, Inc.     

Flow dynamics and erosion rate of a representative karst basin (Upper Aniene River,Central Italy)

Experimental data refer to a preliminary estimate of suspended solid and solute load of a perennial river. The basin is composed almost entirely of bare mesozoic, highly fractured, karstified carbonate rocks of the central Apennine range. The suspended solid load related to stormflow events in 1991 corresponds to about 14,970 t yr^–1. For the same period the solute load is 60,060 t yr^–1 for a mean base flow discharge of 9.4 m³ s^–1. Based on the mean concentration of Ca + Mg in water, the value of dissolution of carbonate rocks of 37.1 m³ km^–2 (equivalent approximately to 0.04 mm yr^–1) was calculated. Physical and chemical variations that occur during storm events indicate the complex dynamic processes in the karst aquifer and the role undertaken by the epikarst as perched water reservoir and by the major conduits that develop through the vadose and saturated zones of the karst system.     

Impact of ancient metal smelting on arsenic pollution in the Pecora River Valley,Southern Tuscany,Italy

A significant As anomaly has been reported in the literature for stream sediments and unlithified Quaternary deposits of the Pecora River valley in Southern Tuscany, extending from the “Colline Metallifere” pyrite-base metals district to the Tyrrhenian Sea. The As anomaly spreads over several square kilometers around a core that exceeds 500 ppm. Several source contributions (from natural to anthropogenic) have been invoked to explain the observed As distribution in the Pecora Valley, including the metal-working industry which was active in this area, particularly in Etrusco-Roman times and in the Middle Ages. In order to evaluate the contribution of ancient mining and metallurgical activities in the Pecora Valley to elevated As concentrations in the environment, a detailed mineralogical and geochemical survey of metallurgical slags and smelted ore minerals was undertaken from six different sites through the Pecora Valley: Poggio Butelli (Etrusco-Roman iron slags); Sata Creek, Arialla, Marsiliana, Forra and Cascata sites (all Medieval base metals slags). The As content of Etrusco-Roman slags is relatively low (few tens of ppm), whereas Medieval slags show variable, but higher amounts of base metals (±Ag) (ranging from tens to tens of thousands ppm) and As (up to 267 ppm, with average contents of about 40 ppm). Arsenic is mostly partitioned in sulfides disseminated through the glassy groundmass rather than in solid solution with the glassy matrix. Remnants of the ore used for base metal and Ag smelting during the Middle Ages had the highest As contents (up to about 1000 ppm).     

Correction: Geochemical and isotopic evidence for upward flow of saline fluid to the Mississippi River Valley alluvial aquifer,southeastern Arkansas,USA

Hydrogeology Journal - A Correction to this paper has been published: https://doi.org/10.1007/s10040-021-02350-y     

Boron isotopic variations in hydrous rhyolitic melts: a case study from Long Valley,California

In this paper, we present boron isotope analyses of variably degassed rhyolitic glasses from Long Valley, California. The following results indicate that pre-eruptive boron isotopic signatures were preserved in degassed glasses: (1) averaged secondary ionization mass spectrometry (SIMS) measurements of H₂O-rich (~3 wt%) melt inclusions from late erupted Bishop Tuff pumice are indistinguishable from positive thermal ionization mass spectrometry (PTIMS) analysis of vesiculated groundmass glass (¹¹B=+5.0±0.9 and +5.4±5, respectively); (2) SIMS spot-analyses on H₂O-poor obsidian (~0.15 wt% H₂O) from younger Glass Mountain Dome YA (average ¹¹B=+5.2±1.0) overlap with compositionally similar late Bishop Tuff melt inclusions; and (3) four variably degassed obsidian samples from the 0.6 ka Mono Craters (H₂O between 0.74 and 0.10 wt%) are homogeneous with regard to boron (average ¹¹B=+3.2±0.8, MSWD=0.4). Insignificant variations in ¹¹B between early and late Bishop Tuff melt inclusion glasses agree with published experimental data that predict minor ¹¹B depletion in hydrous melts undergoing gas-saturated fractional crystallization. Melt inclusions from two crystal-rich post-caldera lavas (Deer Mountain and South Deadman Dome) are comparatively boron-rich (max. 90 ppm B) and have lower ¹¹B values (average ¹¹B=+2.2±0.8 and –0.4±1.0 ) that are in strong contrast to the boron isotopic composition of post-caldera crystal-poor rhyolites (27 ppm B; ¹¹B=+5.7±0.8). These variations in ¹¹B are too large to be caused by pre-eruptive degassing. Instead, we favor assimilation of ¹¹B depleted low-temperature hydrothermally altered intrusive rocks subsequent to fresh rhyolite recharge.Editorial responsibility: J. HoefsAn erratum to this article can be found at     

Chemistry and sulfur isotopic composition of precipitation at Bologna, Italy

Individual and monthly precipitation samples from the polluted atmosphere of Bologna (Emilia-Romagna province) were collected during March 1996 to May 1997 and analyzed for major ions in solution and S isotopes in dissolved SO₄.Weighted mean enrichment factors relative to seawater are found to be 1.0 for Na, 15.2 for K, 105 for Ca, 3.3 for Mg, 17.3 for SO₄ and 663 for HCO⁻₃. Very good positive correlations are observed for the Ca²⁺–Mg²⁺–HCO⁻₃–SO²⁻₄–NO⁻₃ system, indicating that dissolution of Ca (±Mg)-carbonate particles by H₂SO₄ and HNO₃ from combustion of oil and gas is a major process controlling the chemical composition of rain and snow. Na⁺ and Cl⁻ in monthly precipitation derive essentially from sea spray, but the contribution of Na⁺ from continental sources is appreciable in a number of individual rains. NH⁺₄ appears to be on average more abundant in spring and summer precipitation, its main sources being microbial activity in soils and application of fertilizers. K⁺ is probably of continental origin from soil dust.The S isotopic composition of SO₄ is systematically positive, with mean δ³⁴S values of +3.2±1.6‰ (n=40) in individual precipitation and +2.8±1.4‰ (n=12) in monthly precipitation. These isotopic compositions are interpreted in terms of a dominant contribution of S from anthropogenic emissions and subordinate contributions from biogenic and marine sources. Pollutant SO₄ is estimated to have a δ³⁴S value in the range +2.5 to +4.5‰, whereas a distinctive δ³⁴S of −4.5‰ or lower indicates SO₄ from oxidation of biogenic gases.The isotopic and chemical compositions of SO₄ do not depend on wind direction, thus testifying to a mostly local source for pollutant S in the Bologna atmosphere.     

Geochemical and isotopic evidence for upward flow of saline fluid to the Mississippi River Valley alluvial aquifer,southeastern Arkansas,USA

Hydrogeology Journal - Groundwater from the Quaternary Mississippi River Valley Alluvial (MRVA) aquifer in southeastern Arkansas (SE AR), USA, has higher salinity compared to other MRVA...     

Failure mechanisms and pore water pressure conditions: analysis of a riverbank along the Arno River (Central Italy)

Mechanisms of failure occurring in two portions of a riverbank along the Arno River (Central Italy), are investigated in detail starting by a series of periodic field observations and bank profile measurements. Two dominant mechanisms involving the silty sand portion of the bank have been observed: (a) alcove-shaped failure in the middle portion of the bank; (b) slab failure involving the middle–upper bank.

A portion of the riverbank was subject to laboratory (grain size analysis; phase relationship analysis; triaxial tests) and in situ tests (borehole shear tests (BSTs)) to characterise the geotechnical properties of the overbank deposits. Two different procedures of bank stability analysis have been performed: (1) a complete analysis, coupling seepage analysis with the limit equilibrium method; (2) two simplified analyses, through the limit equilibrium method with simple assumptions on pore water pressures distribution.

For the complete analysis, saturated/unsaturated flow within the riverbank was modelled by finite element seepage analysis in transient conditions, using as boundary conditions eight hydrographs with increasing water stage. Riverbank stability analyses have been conducted by the Morgenstern–Price rigorous method, dividing each of the eight hydrographs in 21 time steps and calculating the safety factor for each step. The analysis revealed the occurrence of two possible mechanisms of failure (slab-type and alcove-shaped sliding failures), according to the field observations, related to different river stages and pore water pressures within the riverbank: alcove failures are likely to occur with moderate flow events, while slab failures are favoured by flow events with higher peak river stage.

A first type of simplified analysis, representing critical conditions reached during a rapid flow event, was based on the main hypothesis of the occurrence of a zero pore water pressures zone within the portion of the bank between the low-water stage and the peak stage reached. A second type of simplified analysis was applied in order to represent rapid drawdown conditions following a prolonged flow event (worst case), with the main assumption of total saturation of the material up to the same elevation of the peak river stage. The first simplified analysis has given similar results to the complete seepage/stability analysis, confirming slab-type and alcove-shaped failure as the two main mechanisms of instability, while the second type of simplified analysis has conducted to too conservative results compared to the other previous analyses.

Field observations regarding different characteristic bank geometries in adjacent sub-reaches have been summarised in a conceptual cyclic sketch, that include all the possible paths of bank evolution depending on the succession of river stages reached during flow events and related pore pressure conditions.     

湖北省钟祥市汉江河谷平原区浅层孔隙水的脆弱性评价

以MAPGIS为工作平台,以地下水类型、盖层岩性、地下水埋深为评价指标,利用国际上广泛应用的GOD模型开展了湖北省钟祥市第四系浅层孔隙水的脆弱性评价.研究结果表明:区内浅层孔隙水的脆弱性评分值在0～0.7间,其中极低脆弱性区(评分值=0～0.1)、低脆弱性区(评分值= 0.1～0.3)、中等脆弱性区(评分值=0.3～0.5)、高脆弱性区(评分值=0.5～0.7)和极高脆弱性区(评分值=0.7~10.0)的面积分别占评价区总面积的0.3 %,0.0 %,64.1 %,35.6 %,0. 0 %.换言之,钟祥市汉江河谷平原区浅层孔隙水总体上具有中等脆弱性和高脆弱性,且脆弱性最高的地段几乎全部分布在汉江沿岸.为解决钟祥市工农业发展带来的高污染风险性与地下水具有较高脆弱性这一对明显的矛盾,应加强汉江河谷平原区的地下水资源的管理工作.     

A sulfur isotopic study of alunites from Latium and Tuscany,central Italy

Sulfur isotope analyses were made on 14 alunites from volcanic and sedimentary rocks widely different in chemistry and age from southern Tuscany and northern Latium, central Italy. The ³⁴S values range from +0.7 to +9.6, and appear not to be related to the nature of the host rock. Geological and isotopic evidence suggests that all the alunites formed by supergenic oxidation of sulfides. Sulfides occurring with alunites in the volcanic rocks of Latium can be divided into an isotopically light group of probably magmatic origin (³⁴S=–1.5 to +3.4) and a heavy one with ³⁴S=+6.0 to +10.3, tentatively interpreted as deposited by hydrothermal fluids that leached sulfides of similar ³⁴S/³²S from the deep basement. Such an interpretation is consistent with recent studies indicating that in the perityrrhenian belt of Latium exists a continuation, at depth, of the Tuscan stratigraphic series, rich in sulfides with ³⁴ from +6 to +12.     

Petrology and Petrogenesis of the Latera Caldera, Central Italy

At least 8 km³ of felsic ignimbrites and high-K silica-undersaturatedlavas and tephra were erupted from the Latera caldera between250 and 150 ka. Four distinct periods of explosive eruptions(at about 232, 206, 195, and 156 ka) produced ignimbrite sequencesthat show an upward compositional progression from trachyteand differentiated phonolite to less evolved phonolite. Duringthe last two of these periods, the tuffs grade upward from phonoliteto tephriphonolite. The stratigraphy indicates that eruptionssampled magmas that were stratified downward from trachyte andphonolite to tephriphonolite, and the compositional cyclicitysuggested by the timing of the eruptions implies an unusualcontemporaneity of silica-saturated and -undersaturated compositions. At Latera, pumice fragments in the same deposit can exhibitup to 10-fold differences in vesicularity and crystal content(from <5 to >50 vol.% phenocrysts). These clasts, in conjunctionwith glassbearing syenite and skarn xenoliths, represent a rangeof progressively crystallized magmas that were quenched at theinstant of their eruptive entrainment. The syenites compriseeutectic mineral assemblages with high percentages of titanite,apatite, and melanite garnet as accessory minerals. Least-squaresmodels based on major element and compatible trace element (e.g.,Ba and Sr) abundances of the pumices and syenite indicate thatthe fractionation of plagioclase and sanidine largely controlledthe liquid lines of descent for phonolite and trachyte, respectively.Additional mineral phases that may have contributed to magmaticdifferentiation include fassaitic diopside, leucite, biotite,apatite, and alkali amphibole. Models further imply that tephriphonoliticliquids required roughly 70% crystallization of tephritic orbasanitic parent magmas, whereas the evolved phonolitic liquidswere obtained after the removal of >85% of the above mineralassemblage. The commonly aphyric trachytic tuffs represent themost evolved derivatives. Despite the limited range in major element contents, trace elementsvary considerably among the different pumice types and syenites.Large ranges in Rb/Sr, Nb/Ta, Zr/Hf, La/Yb, and Ba/Th reflectthe selective partitioning of some elements into accessory phases.However, the variations of B, Sc, Rb, Nb, Hf, Y, and Yb cannotbe explained completely by crystal fractionation. Syenite compositions,for example, bracket the range of most elements in all pumicetypes, and chemical models demonstrate that processes operatingalong the chamber margins could have greatly influenced thebehavior of trace elements in the evolved liquids. Plausiblemechanisms that might have accompanied crystal fractionationin these magmas include the mixing of several magma batches,and the possible dilution of central reservoir magmas by back-mixingwith fractionated liquids or with CO₂-rich fluids released fromskarns. *Present Address: Bureau of Economic Geology, Mineral Studies Laboratory, University of Texas, Austin, Texas 78713-7508     

Major,trace element and Sr isotopic composition of lavas from Vico volcano (Central Italy) and their evolution in an open system

Major, trace element and Sr isotopic compositions have been determined on 21 lava samples from Vico volcano, Roman Province, Central Italy. The rocks investigated range from leucite tephritic phonolites to leucite phonolites and trachytes. Trace element compositions are characterized by high enrichments of incompatible elements which display strong variations in rocks with a similar degree of evolution. Well-defined linear trends are observed between pairs of incompatible trace elements such as Th-Ta, Th-La, Th-Hf. A decrease of Large Ion Lithophile (LIL) elements abundance contemporaneously with the formation of a large central caldera is one of the most prominent characteristics of trace element distribution. Sr isotope ratios range from 0.71147 to 0.71037 in the pre-caldera lavas and decreases to values of 0.70974–0.70910 in the lavas erupted after the caldera collapse. Theoretical modelling of geochemical and Sr isotopic variations indicates that, while fractional crystallization was an important evolutionary process, AFC and mixing also played key roles during the evolution of Vico volcano. AFC appears to have dominated during the early stages of the volcanic history when evolved trachytes with the highest Sr isotope ratios were erupted. Mixing processes are particularly evident in volcanites emplaced during the late stages of Vico evolution. According to the model proposed, the evolution of potassic magmas emplaced in a shallow-level reservoir was dominated by crystal fractionation plus wall rock assimilation and mixing with ascending fresh mafic magma. This process generated a range of geochemical and isotopic compositions in the mafic magmas which evolved by both AFC and simple crystal liquid fractionation, producing evolved trachytes and phonolites with variable trace element and Sr isotopic compositions.